Declutching device in a sewing machine



Jan. 20, 1970 TADAO ASANO ET AL 3,490,708

DECLUTCHING DEVICE IN A SEWING MACHINE Filed Feb. 5, 1968 2 Sheets-Sheet l TADAO Asmo AW sameam mam Jan. 20, 1970 TADAO ASANO ET AL 3,490,703

DECLUTCHING DEVICE IN A SEWING MACHINE 2 Sheets-Sheet 2 Filed Feb. 5, 1968 M w w s & m

BY wmwm p United States Patent 3,490,708 DECLUTCHIN G DEVICE IN A SEWING MACHINE Tadao Asano and Suehiko Murata, Kariya, Japan, as-

signors to Aisin Seiki Kabushiki Kaisha, Kariya, Aichi Prefecture, Japan Filed Feb. 5, 1968, Ser. No. 703,136 Claims priority, application Japan, Feb. 18, 1967, 42/ 13,783 Int. Cl. F16d 13/08; B6511 79/00 US. Cl. 242-20 3 Claims ABSTRACT OF THE DISCLOSURE A declutching device for sewing machine provided with an arm shaft and a hand wheel or flywheel for driving said arm shaft, which comprises a helical clutch spring wound around a bushing of the arm shaft, said clutch spring being wound in the direction reverse to the drection of normal rotation of the flywheel, so that the coil of spring is expanded during the normal rotation of the flywheel, thereby making firm engagement of the arm shaft bushing with the inner wall of the hub of said flywheel, and means is provided for decreasing the coil diameter of said clutch spring so that the flywheel is allowed to be rotated freely without driving the arm shaft during the thread winding operation by declutching the same.

In conventional sewing machines, in effecting the operation of the thread winder as driven from the flywheel, it is necessary that the flywheel is declutched. In the known constructions, however, there is trouble and disadvantage caused by the fact that the arm is unexpectedly rotated at the time of effecting the thread winding mainly due to the users failure in declutching the flywheel.

The principal object of the present invention is to provide an improved declutch device, wherein the clutch connecting the flywheel with the arm shaft bushing is automatically declutched upon shifting the thread winder assembly toward its operative osition, while holding the flywheel freely rotatable, so that the above mentioned disadvan age may be removed.

Other objects and advantages of the invention will become apparent from the following description, when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a perspective view of the right-hand portion of a sewing machine arm of the present invention;

FIGURE 2 is a longitudinal section of the arm shown in FIGURE 1;

FIGURE 3 is an end view, partly in section, as seen from the right of FIGURE 2;

FIGURE 4 is a detail showing a clutch spring employed in the device according to this invention; and

FIGURE 5 is another detail showing cross-sectional view of a one-way power transmission for preventing free rotation of the flywheel when it rotates in the reversed direction.

Referring to the drawing, on an upper shaft or arm shaft 1 of a sewing machine, there is a fixedly mounted bushing 2, on which the hub of a flywheel or hand wheel 3 is loosely moun ed. The bushing 2 is surrounded by a clutch spring 4, which is wound in the direction reverse to the normal direction of rotation N (FIG. 3) of said flywheel 3. One end 4a of the clutch spring 4 is fixed in a notch 2b of the bushing 2, and the other end 4b extends outwardly through an annular slot 3b of the fly wheel 3, making a free end formed into a hook, as shown in FIG. 2. The outer peripheral face of the coil of spring 4- is in frictional contact with the inner wall 3a of the hub of the flywheel 3, whereby during the normal opera- 3,490,708 Patented Jan. 20, 1970 tion of the sewing machine the outer diameter of the coil of the spring is increased, so that the friction between said spring and the inner wall 3a of the flywheel 3 will be increased accordingly. 6 is a clamp screw for preventing demounting of the flywheel 3.

Betwen the flywheel 3 and the bushing 2 there is a oneway power transmission comprising a small steel ball 5 inserted in a tapered peripheral slot 20 (FIG. 5) provided in the bushing 2. When the flywheel 3 is rotating in the normal direction N, the ball 5 is in the wider space of the slot 2c, as shown in dotted line in FIG. 5, whilst when the flywheel 3 rotates in the reverse direction the ball 5 is shifted toward the narrower space as shown in solid line, so that the transmission of power is established between the flywheel 3 and the bushing 2 fixed to the arm shaft 1, and any free rotation of the flywheel 3 may be prevented in case of the reverse rotation thereof.

On an arm 7 of the sewing machine, a bracket 8 is secured by means of set screws 9. On said bracket 8 there is slidably mounted a clutch control bar 10 by means of stepped pins 11 which pass through an oblong guide slot 10a in the control bar 10, and said control bar 10 is normally biassed downwardly by means of a tension spring 12. When the control bar 10 is lifted against the action of the spring 12, the upper end 10b thereof is adapted to engage with the free end 4b of the clutch spring 4. 13 is a rotatable thread winder which is mounted upon a shaft 14 pivoted to a motor cover 15. Onto said shaft 14 there is securely mounted a crank arm 17, of which the upper edge 17a is normally abutting against the lower end of the control bar 10, and the crank arm 17 is adapted to lift the control bar 10 in association with the movement of the thread winder 13 into its operative position shown at B in FIG. 3, in which position the thread winder 13 is in operative engagement with the periphery of the flywheel 3. 18 is a V-belt connecting a drive shaft 19 of the driving motor and a V- pulley forming a part of the flywheel 3.

As hereinbefore described, the coil of the clutch spring 4 is wound in the direction reverse to the normal rotation of the flywheel 3, so that the coil of said spring 4 normally has a tendency of expanding outwardly, thereby keeping the periphery thereof in strong frictional engagement with the inner wall 3a of the hub of the flywheel 3 in case of the normal rotation thereof and, hence, the rotation of the flywheel 3 will be transmitted to the arm shaft 1 through the bushing 2.

When it is desired to bring the thread winder 13 into operation, holding the flywheel 3 in free rotation, the thread winder 13 in the inoperative position A is shifted toward the operative position B (FIG. 3), bringing it into engagement with the rotating flywheel 3, whereby the control bar 10 will be lifted against the action of the tension spring 12 by means of the crank arm 17. Accordingly, the upper end 10b of the control bar 10 will pull the free end 4b of the spring 4 in the direction of arrow R, i.e. in the direction of initial winding of the coil of spring, shifting thereby the free end 4b of the spring from the position shown in chain line to the position shown in solid line in FIG. 4, decreasing thereby the diameter of the coil of spring, thereby releasing the frictional engagement of the periphery of the coil of spring with the inner wall 3a of the hub of the flywheel 3, so that the latter will perform a free rotation on the bushing 2, without transmitting power to the arm shaft 1.

To restart the normal operation of the sewing machine after finishing the thread winding operation, the thread winder 13 is returned to the initial inoperative position A, thereby lowering the control bar 10 by the action of the tension spring 12 and releasing the engagement of the upper end 10b thereof with the free end 4b of the spring 4, so that the latter will return to the initial position, re-

establishing the frictional engagement of the periphery of the coil of spring with the inner wall 3a of the flywheel 3, whereby the normal rotation of the flywheel 3 will be transmitted to the arm shaft 1.

From the foregoing it will be seen according to the present invention that when the flywheel 3 is utilized for effecting the thread winding operation the latter is put into free rotation without transmitting any motion to the arm shaft 1. Therefore, there would not occur any trouble caused by undesired operation of the arm shaft 1 due to insufficient release of the stop motion at the time of the thread winding operation.

What we claim is:

1. In a sewing machine provided with an arm shaft, a bushing fixed to said arm shaft, a flywheel loosely mounted on said bushing for transmitting rotation thereof to the latter, and a thread winder assembly adapted to be driven by said flywheel, a declutching device comprising a helical clutch spring wound around said bushing, the coil of said clutch spring being wound in the direction reverse to the direction of normal rotation of said flywheel, the arrangement being such that the diameter of said coil of spring is increased during the normal rotation of said flywheel, and means controlled by the movement of said thread winder and adapted for decreasing the diameter of the coil of said clutch spring, thereby declutching the said flywheel from said bushing so as to allow the free rotation of said flywheel during the thread winding operation.

2. Declutching device for a sewing machine as recited in claim 1, wherein one end of said helically wound clutch spring is secured to said bushing and the other free end of said clutch spring is extended outwardly through an annular slot in the flywheel, and a control bar adapted to be actuated by the movement of said thread winder assembly is provided for pulling said free end of the clutch spring, so as to decrease the diameter of the coil of spring, thereby allowing the free rotation of said flywheel.

3. A declutching device for a sewing machine as recited in claim 1, wherein there is provided a one-way power transmission device between said bushing and the flywheel adapted to allow the transmission of power from the flywheel to the bushing when the flywheel is rotated in the direction reverse to the normal rotation.

References Cited UNITED STATES PATENTS 259,383 6/1882 Goodwin 24220 3,058,437 10/1962 Iida. 3,123,034 3/1964 Okazaki 112-220 3,388,681 6/1968 Fujita 112-220 3,408,882 11/1968 Bialy.

MERVIN STEIN, Primary Examiner WERNER H. SCHROEDER, Assistant Examiner US. Cl. X.R. 

